I have been editing on Davinci Resolve for about 4 months and I am now adding music on my timeline. Can someone explain to me how to fade music up and down on the timeline. I am sure this is easy.... I have the Davinci Resolve manual but cannot find the answers I need!

Yes, it is an easy task. If you already put in a music track into one of your audio channels, go to the Edit tab. Select the music track by clicking on it in the timeline move your cursor to the upper left corner of track in the timeline and a small marker should appear. Grab this marker and move it to the right, so far as the fade in is wanted. There is also a small circle appearing which allows you to adjust the attack curve.

If you want more control and finer settings, look into animating your volume with keyframes and curves.